To evaluate the impact of a mild increment in blood pressure level on endothelial function, we evaluated 61 healthy volunteers (24 women, 37 men, and aged 35-50 years). All subjects underwent a blood chemistry panel to exclude any metabolic abnormalities and were submitted to a Doppler ultrasound of the brachial artery to assess endothelial function. We assessed the endothelial response to reactive hyperaemia and exogenous nitric oxide administration considering an increase in systolic blood pressure (SBP) at each 10-mm Hg interval. Our study population was divided as follows: SBP <115 mm Hg (SG1, n=13), SBP > or =115 mm Hg and <125 mm Hg (SG2, n=20), SBP > or = 125 mm Hg and <135 mm Hg (SG3, n=13) and SBP > or = 135 mm Hg and < 140 mm Hg (SG4, n=15). We found a significant difference in flow-mediated dilation among SG2, SG3 and SG4, 16.2+/-5.6, 13.4+/-5.2 and 11.5+/-3.6%, P<0.05, respectively). After nitrate administration, we observed a nonsignificant decrease in brachial artery dilation among groups, P=0.217. Our data showed in a healthy normotensive population, without any risk factor for atherosclerotic disease that small increases in SBP but not in diastolic blood pressure may impair endothelial function even in subjects considered as high-normal, meaning that this population deserves more attention than usually ascribed to intervene and prevent complications, as endothelial dysfunction may represent an early change in those who develop hypertension later in life.